1. Field of the Invention
The present invention relates to bone resorption suppressing agents comprising a milk-derived basic cystatin and/or milk-derived basic cystatin decomposition product as an effective component, and in particular to bone resorption suppressing agents to be used for the prevention and treatment of bone joint diseases or periodontal diseases.
The present invention also relates to drinks, food products and feed in which a milk-derived basic cystatin and/or milk-derived basic cystatin decomposition product are admixed to provide an activity to prevent and treat bone joint diseases or periodontal diseases. In particular, the present invention relates to drinks, food products and feed to which a highly absorbable calcium composition and vitamin D and/or vitamin K, in addition to a milk-derived basic cystatin and/or milk-derived basic cystatin decomposition product, are admixed to provide an activity to prevent and treat bone joint diseases or periodontal diseases.
2. Description of the Related Art
In recent years, the number of people suffering from bone joint diseases such as osteoporosis and rheumatism has been on the rise because of the aging population. Bone formation and bone resorption continuously take place in bone tissue and are well balanced in early life, but the balance is lost with an increase in bone resorption with aging for various reasons. If this unbalance continues for a long period of time, the bone tissue becomes fragile, which results in bone diseases such as osteoporosis, bone fractures and lumbago. It is believed that if this uncoupling can be prevented, osteoporosis, bone fractures, lumbago or the like can be prevented.
Conventional methods to prevent and treat bone diseases by preventing the uncoupling include (1) dietary supplementation of calcium, (2) moderate exercise, (3) sunbathing, and (4) therapy by medicines.
For dietary supplementation, calcium salts such as calcium carbonate and calcium phosphate, natural calcium supplements such as bovine bone powders, egg shells and fish bone powders are used. To date, such food products and food materials have been used exclusively for calcium supplementation.
For moderate exercise, moderate running or walking are highly recommended. However, even moderate exercise is difficult for people who are physically weak and, not to mention, almost impossible for elderly people who are confined to bed.
Sunbathing is good for the supplementation of activated vitamin D3, but not sufficient by itself
As for therapeutic medicines, 1xcex1-hydroxy vitamin D3, calcitonin preparations or the like are known to be effective to cure and treat osteoporosis. Calcitonin preparations are medicinal hormone preparations. Safe substances for calcitonin obtainable from food materials have not been presently studied. Calcitonin is difficult to prepare in bulk and to provide as a safe food material since animal tissues, cells, blood, or urine have to be used as raw materials.
It is believed that rheumatism, a joint disease, can be prevented and treated by suppressing bone resorption since it is associated with the bone resorption.
In recent years, periodontal diseases have also become a serious social problem. Unlike dental caries, periodontal diseases weaken the roots of teeth, which makes even healthy teeth useless. Today, many people develop symptoms of periodontal diseases. Periodontal diseases can be more serious than dental caries.
Today, means to prevent periodontal diseases are to prevent the growth of causative microorganisms, for example, the removal of dental plaque or gargling using mouthwashes containing antibacterial agents or the like. However, these means seem to be less effective for highly developed symptoms. Namely, in the late stage of periodontal diseases, the alveolar bone mass decreases, and once alveolar bones are lost, unregenerable symptoms occur. Teeth loss due to periodontal diseases then makes eating difficult and painful, which is disturbing in everyday life. Thus, there is a need for effective means for the prevention and treatment of periodontal diseases.
However, so far, there is no agent available for the prevention and treatment of periodontal diseases which effectively suppresses a decrease in alveolar bone mass.
Thus, like osteoporosis, periodontal diseases have become a serious social problem. Therefore, an effective treatment for periodontal diseases is will greatly contribute to people""s health, and accordingly is necessary.
The present inventors intensively searched for a milk whey fraction having osteoblast growth stimulating activity, bone resorption suppressing activity and bone strengthening activity, in order to obtain a material which can be used for the prevention and treatment of bone junction diseases and periodontal diseases. Namely, the present inventors fractionated proteins in milk, in particular milk whey, in an attempt to obtain a fraction having a bone resorption suppressing activity, and found a bone strengthening activity in a protein-peptide mixture which was obtained by treating a water soluble fraction of whey proteins with a reverse osmotic membrane or electrodialysis to remove whey-derived salts (Japanese Patent Laid-open No. 4-183371). Furthermore, the present inventors found that a fraction obtained by treating an aqueous solution of this protein-peptide mixture with ethanol, heat, salts or an ultrafiltration membrane has a bone strengthening activity (Japanese Patent Laid-open No. 5-176715, Japanese Patent Laid-open No. 5-320066). The present inventors also found that basic proteins present in milk in trace amounts have an osteoblast collagen synthesis stimulating activity and bone resorption suppressing activity (Japanese Patent Laid-open No. 8-151331).
Cystatin is a cysteine protease inhibitor which inhibits proteolytic activity of cysteine proteases having an SH group in the active center and is found in animal tissues, cells and urine. A virus growth inhibiting activity was recognized as a useful activity of cystatin (Biochem. Biophys. Res. Commun., Vol. 127, p. 1072, 1985).
Japanese Patent Laid-open No. 2-223529 describes the use of cystatin as anti-allergic agents and as therapeutic agents for bone diseases in the form of an injectable preparation, suppository, nasal powder or the like. More specifically, it described a test result wherein the blood calcium level was reduced in rats by intravenously injecting rats with rat-derived cystatin prepared by genetic engineering. However, one cannot readily conclude that cystatin has an activity to prevent and treat bone joint diseases such as osteoporosis and rheumatism, solely from this result.
Furthermore, until now, a bone resorption suppressing agent comprising a milk-derived basic cystatin and/or milk-derived basic cystatin decomposition product which is effective by administration orally but not necessarily intravenously, as an effective component, are not known. Also, a drink, food product or feed which contains such components in higher concentrations, along with calcium and vitamins, and can be administered orally is not known.
Although the present inventors previously applied for a patent (Japanese Patent Laid-open No. 7-126294) on a cysteine protease inhibitor other than the milk-derived basic cystatin, the bone resorption suppressing activity of the milk-derived basic cystatin of the present invention is higher than that of said inhibitor.
The present inventors tried to isolate and purify an active substance from of basic protein fraction having a bone resorption suppressing activity, identified the resulting substance, and found this substance is a milk-derived basic cystatin. Furthermore, the present inventors found that the milk-derived basic cystatin has a particularly high bone resorption suppressing activity as compared with cystatins from other origins. Further, the present inventors found that a decomposition product of the milk-derived basic cystatin also has a high bone resorption suppressing activity, and thus completed the present invention.
Accordingly, the objective of the present invention is to provide bone resorption suppressing agents comprising the milk-derived cystatin and/or milk-derived cystatin decomposition product as an effective component, and drinks, food products and feeds in which the milk-derived cystatin and/or milk-derived cystatin decomposition product are admixed to provide a bone resorption suppressing activity.
Further, the present invention is industrially useful because a highly safe milk-derived basic cystatin can be prepared in bulk from a food material, i.e., milk, and admixed as a safe food material.
The present inventors found that a milk-derived basic cystatin and a milk-derived basic cystatin decomposition product have an excellent bone resorption suppressing activity and thus completed the present invention. Namely, the present invention provides bone resorption suppressing agents comprising the milk-derived basic cystatin and/or milk-derived basic cystatin decomposition product as an effective component. Further, the present invention can provide a bone resorption suppressing activity to drinks, food products and feed by admixing them with the milk-derived basic cystatin and/or milk-derived basic cystatin decomposition product. Further, the present invention can provide both a bone resorption suppressing activity and bone formation stimulating activity to drinks, food products and feed by admixing them with the milk-derived basic cystatin and/or milk-derived basic cystatin decomposition product with a highly absorbable calcium component and vitamin D and/or vitamin K.
More specifically, based on the above mentioned bone resorption suppressing activity of the milk-derived basic cystatin and/or milk-derived basic cystatin decomposition product, bone resorption suppressing agents can be provided, which comprises milk-derived basic cystatin and/or milk-derived basic cystatin decomposition product as an effective component for the prevention and treatment of bone joint diseases or periodontal diseases. Also, drinks, food products and feeds having activities to prevent and treat bone joint diseases or periodontal diseases can be provided by admixing them with milk-derived basic cystatin and/or milk-derived basic cystatin decomposition products.
The present invention provides a bone resorption suppressing activity to drinks, food products and feed by admixing the safe milk-derived basic cystatin and/or milk-derived basic cystatin decomposition product prepared using cow""s milk, a food product, as a raw material.
Examples of milk to be used as a raw material for the milk-derived basic cystatin include raw milk, powdered milk, skimmed milk, and reconstituted milk. The milk-derived basic cystatin can be obtained from these milk materials by heating, salt treatment, ethanol treatment, various chromatographic methods, such as ion exchange chromatography and gel filtration chromatography, treatment with an ultrafiltration membrane, or the like.
A milk-derived basic cystatin decomposition product of the present invention is a peptide mixture prepared by restrictively decomposing the abovementioned milk-derived basic cystatin with proteases, such as trypsin, chymotrypsin, pepsin, papain, kallikrein, cathepsin, thermolysin, and B8 protease.
In the present invention, the abovementioned milk-derived basic cystatin and/or milk-derived basic cystatin decomposition product are added to drinks and food products to provide them with bone resorption suppressing activity. Examples of such drinks and food products include milk, milk drinks, juices, jellies, biscuits, breads, noodles, and sausages. Bone joint diseases, such as osteoporosis and rheumatism, and periodontal diseases can be prevented or treated by ingesting such drinks and food products to which the bone resorption suppressing activity is provided.
In the present invention, a milk-derived basic cystatin and/or milk-derived basic cystatin decomposition product are used as medicines, or admixed into drinks, food products and feed as an effective component for the prevention or treatment of bone joint diseases, such as osteoporosis and rheumatism, in an amount of about 8 xcexcg to 10 mg per day for an adult, to be administered in divided doses. In particular, the milk-derived basic cystatin and/or milk-derived basic cystatin decomposition product are preferably admixed into drinks, food products or feed, at a concentration of more than 4 xcexcg % so as to easily attain the abovementioned dosage.
In the present invention, a milk-derived basic cystatin and/or milk-derived basic cystatin decomposition product are used as medicines, or admixed into drinks, food products and feed as an effective component for the prevention or treatment of periodontal diseases, for example in a form of tooth paste, mouth wash, candy, chewing gum or troche by bringing them into contact with the tooth surface in an amount of about 8 xcexcg to 10 mg per day for an adult to be administered in divided doses.
A highly absorbable calcium salt having an excellent absorbability is preferably admixed into bone resorption suppressing agents, drinks, food products and feed of the present invention. Examples of the highly absorbable calcium salt include calcium chloride, calcium carbonate, calcium lactate, egg shells and substances containing milk-derived calcium. Effective components for bones, such as vitamin D and vitamin K, can also be admixed. In such cases, the desirable synergistic effect of the bone formation stimulating activity provided by admixing the abovementioned highly absorbable calcium and vitamins with the bone resorption suppressing activity provided by a milk-derived basic cystatin and/or milk-derived basic cystatin decomposition product can be attained.
Milk-derived basic cystatin has bone resorption suppressing activity when ingested as an admixture in food products and is an excellent material for food processing because of its good heat stability.
The present invention will be explained in detail in the following examples and test examples.